1. Field of the Invention
The present invention relates to a steering apparatus for use in a vehicle steering system and, more particularly, to a torque sensor for use in a vehicle steering system.
2. Description of Related Art
In known power steering systems an input force from a manually operated steering wheel for turning steered wheels of a vehicle may be assisted by an input from a motor driver. In such a steering system, it is known to provide a sensor for sensing a torque input from the steering wheel, where the sensed torque is provided as an input signal for a controller controlling the motor driver. The input provided by the motor driver may be controlled so as to provide a predetermined steering assist for a given level of input torque from the steering wheel.
Various constructions have been proposed for providing a measurement of the sensed torque input to the steering wheel. In a common sensing application, a relative movement between an input shaft and an output shaft is sensed. In particular, the input and output shafts may be connected by an elastically deformable member having predetermined torsional characteristics that permit relative rotation between the input and output shafts, where the relative rotation of the input and output shafts is indicative of the torque input.
U.S. Patent Application Publication No. 2004/0011138 A1 discloses a sensor for sensing a steering column torsion in which a programmable Hall effect sensor may be mounted in an air gap defined by two ferromagnetic collectors forming a structure for rotating relative to a structure provided with a plurality of magnets to provide a magnetic flux variation indicative of an applied torque, as sensed by the Hall effect sensor.
U.S. Patent Application Publication No. 2003/0062215 A1 discloses a power steering system including a sensor located between a ring shaped centrally located magnet and a magnetic body comprising a couple of magnetic yokes. The magnetic body changes a magnetic flux density of a magnetic circuit when a relative position between the magnetic body and the permanent magnet is changed by a torque applied to a steering shaft.
There continues to be a need for a torque sensing element capable of providing an accurate indication of a torque applied to a steering wheel of a vehicle, and which can provide an indication of applied torque independently of a rotational position of the steering wheel.